Unique arbuscular mycorrhizal fungal communities uncovered in date palm plantations and surrounding desert habitats of Southern Arabia

The main objective of this study was to shed light on the previously unknown arbuscular mycorrhizal fungal (AMF) communities in Southern Arabia. We explored AMF communities in two date palm (Phoenix dactylifera) plantations and the natural vegetation of their surrounding arid habitats. The plantations were managed traditionally in an oasis and according to conventional guidelines at an experimental station. Based on spore morphotyping, the AMF communities under the date palms appeared to be quite diverse at both plantations and more similar to each other than to the communities under the ruderal plant, Polygala erioptera, growing at the experimental station on the dry strip between the palm trees, and to the communities uncovered under the native vegetation (Zygophyllum hamiense, Salvadora persica, Prosopis cineraria, inter-plant area) of adjacent undisturbed arid habitat. AMF spore abundance and species richness were higher under date palms than under the ruderal and native plants. Sampling in a remote sand dune area under Heliotropium kotschyi yielded only two AMF morphospecies and only after trap culturing. Overall, 25 AMF morphospecies were detected encompassing all study habitats. Eighteen belonged to the genus Glomus including four undescribed species. Glomus sinuosum, a species typically found in undisturbed habitats, was the most frequently occurring morphospecies under the date palms. Using molecular tools, it was also found as a phylogenetic taxon associated with date palm roots. These roots were associated with nine phylogenetic taxa, among them eight from Glomus group A, but the majority could not be assigned to known morphospecies or to environmental sequences in public databases. Some phylogenetic taxa seemed to be site specific. Despite the use of group-specific primers and efficient trapping systems with a bait plant consortium, surprisingly, two of the globally most frequently found species, Glomus intraradices and Glomus mosseae, were not detected neither as phylogenetic taxa in the date palm roots nor as spores under the date palms, the intermediate ruderal plant, or the surrounding natural vegetation. The results highlight the uniqueness of AMF communities inhabiting these diverse habitats exposed to the harsh climatic conditions of Southern Arabia

Agronomic Management of Indigenous Mycorrhizas

Many of the advantages conferred to plants by arbuscular mycorrhiza (AM) are associated to the ability of AM plants to explore a greater volume of soil through the extraradical mycelium. Sieverding (1991) estimates that for each centimetre of colonized root there is an increase of 15 cm3 on the volume of soil explored, this value can increase to 200 cm3 depending on the circumstances. Due to the enhancement of the volume of soil explored and the ability of the extraradical mycelium to absorb and translocate nutrients to the plant, one of the most obvious and important advantages resulting from mycorrhization is the uptake of nutrients. Among of which the ones that have immobilized forms in soil, such as P, assume particular significance. Besides this, many other benefits are recognized for AM plants (Gupta et al, 2000): water stress alleviation (Augé, 2004; Cho et al, 2006), protection from root pathogens (Graham, 2001), tolerance to toxic heavy metals and phytoremediation (Audet and Charest, 2006; Göhre and Paszkowski, 2006), tolerance to adverse conditions such as very high or low temperature, high salinity (Sannazzaro et al, 2006), high or low pH (Yano and Takaki, 2005) or better performance during transplantation shock (Subhan et al, 1998). The extraradical hyphae also stabilize soil aggregates by both enmeshing soil particles (Miller e Jastrow, 1992) and producing a glycoprotein, golmalin, which may act as a glue-like substance to adhere soil particles together (Wright and Upadhyaya, 1998). Despite the ubiquous distribution of mycorrhizal fungi (Smith and Read, 2000) and only a relative specificity between host plants and fungal isolates (McGonigle and Fitter, 1990), the obligate nature of the symbiosis implies the establishment of a plant propagation system, either under greenhouse conditions or in vitro laboratory propagation. These techniques result in high inoculum production costs, which still remains a serious problem since they are not competitive with production costs of phosphorus fertilizer. Even if farmers understand the significance of sustainable agricultural systems, the reduction of phosphorus inputs by using AM fungal inocula alone cannot be justified except, perhaps, in the case of high value crops (Saioto and Marumoto, 2002). Nurseries, high income horticulture farmers and no-agricultural application such as rehabilitation of degraded or devegetated landscapes are examples of areas where the use of commercial inoculum is current. Another serious problem is quality of commercial available products concerning guarantee of phatogene free content, storage conditions, most effective application methods and what types to use. Besides the information provided by suppliers about its inoculum can be deceiving, as from the usually referred total counts, only a fraction may be effective for a particular plant or in specific soil conditions. Gianinazzi and Vosátka (2004) assume that progress should be made towards registration procedures that stimulate the development of the mycorrhizal industry. Some on-farm inoculum production and application methods have been studied, allowing farmers to produce locally adapted isolates and generate a taxonomically diverse inoculum (Mohandas et al, 2004; Douds et al, 2005). However the inocula produced this way are not readily processed for mechanical application to the fields, being an obstacle to the utilization in large scale agriculture, especially row crops, moreover it would represent an additional mechanical operation with the corresponding economic and soil compaction costs. It is well recognized that inoculation of AM fungi has a potential significance in not only sustainable crop production, but also environmental conservation. However, the status quo of inoculation is far from practical technology that can be widely used in the field. Together a further basic understanding of the biology and diversity of AM fungi is needed (Abbott at al, 1995; Saito and Marumoto, 2002). Advances in ecology during the past decade have led to a much more detailed understanding of the potential negative consequences of species introductions and the potential for negative ecological consequences of invasions by mycorrhizal fungi is poorly understood. Schwartz et al, (2006) recommend that a careful assessment documenting the need for inoculation, and the likelihood of success, should be conducted prior to inoculation because inoculations are not universally beneficial. Agricultural practices such as crop rotation, tillage, weed control and fertilizer apllication all produce changes in the chemical, physical and biological soil variables and affect the ecological niches available for occupancy by the soil biota, influencing in different ways the symbiosis performance and consequently the inoculum development, shaping changes and upset balance of native populations. The molecular biology tools developed in the latest years have been very important for our perception of these changes, ensuing awareness of management choice implications in AM development. In this context, for extensive farming systems and regarding environmental and economic costs, the identification of agronomic management practices that allow controlled manipulation of the fungal community and capitalization of AM mutualistic effect making use of local inoculum, seem to be a wise option for mycorrhiza promotion and development of sustainable crop production

Propriedades psicométricas da Dutch Fatigue Scale e Dutch Exertion Fatigue Scale: versão brasileira Propiedades psicométricas de la Dutch Fatigue Scale y Dutch Exertion Fatigue Scale: versión Brasileña Psychometric properties of the Dutch Fatigue Scale and the Dutch Exertion Fatigue Scale: Brazilian version

Fadiga é uma resposta humana em diversas situações agudas e crônicas e também na população geral. Este artigo relata estudo realizado para estimar confiabilidade e validade da Dutch Fatigue Scale (DUFS) e da Dutch Exertion Fatigue Scale (DEFS) adaptadas para o Brasil. Trezentos pacientes ambulatoriais com insuficiência cardíaca e 64 voluntários responderam a DUFS e a DEFS vertidas para o português. Análise fatorial sobre o conjunto de itens das duas escalas produziu solução com um fator para cada escala (variância explicada = 53,9%) e boas estimativas de confiabilidade pelo alfa de Chronbach (DUFS=0,85 e DEFS=0,92) foram obtidas. Na amostra de pacientes, os escores nas escalas foram positivamente associados com a classe funcional da insuficiência cardíaca (DUFS e DEFS p=0,000), com os escores de depressão (DUFS r s=0,63; p=0,00 e DEFS r s=0,55; p=0,00) e com distúrbio de sono (DUFS e DEFS p=0,000). As versões brasileiras mostraram propriedades semelhantes as das escalas originais.<br>Fatiga es una respuesta humana en muchas situaciones agudas e crónicas e también en la populación general. Este artículo relata estudio realizado para estimar la confiabilidad e validad de la Dutch Fatigue Scale (DUFS) y de la Dutch Exertion Fatigue Scale (DEFS) adaptadas para o Brasil. Trescientos pacientes con insuficiencia cardiaca y 64 voluntarios respondieran a la DUFS y DEFS vertidas para lo portugués. El análisis factorial de los ítems ha producido solución con un factor para cada escala (variancia explicada = 53,9%) y buenas estimativas de confiabilidad por lo alfa de Chronbach (DUFS=0,85 e DEFS=0,92) fueron obtenidas. En la muestra de pacientes, las puntuaciones en las escalas fueron positivamente asociadas con la clase funcional de la insuficiencia cardiaca (DUFS y DEFS p=0,000), los escores de depresión (DUFS r s=0,63; p=0,00 y DEFS r s=0,55; p=0,00), y con las alteraciones del sueno (DUFS y DEFS p=0,000). Las versiones brasileras mostraran propiedades similares a las das escalas originais.<br>Fatigue is a human response in varied acute and chronic conditions and also in general population. This article reports a study conducted to estimate reliability and validity of the Dutch Fatigue Scale (DUFS) and the Dutch Exertion Fatigue Scale (DEFS) adapted for Brazilian use. Three-hundred heart failure patients and 64 healthier volunteers answered the DUFS and DEFS translated into Portuguese. Factorial analysis of DUFS and DEFS items yield a solution with one factor for each scale (explained variance = 53.9%), and good reliability estimates were obtained by the Chronbach's alpha (DUFS=.85 e DEFS=.92). In the patient sample, scales scores were positively associated with heart failure functional class (DUFS and DEFS p=.00), depression scores (DUFS r s=.63; p=.00 and DEFS r s=.55; p=.00), and sleep disturbance (DUFS and DEFS p=.00). Brazilian versions of DUFS and DEFS presented psychometric properties similar to those of the original ones

C: N: P stoichiometry and specific growth rate of clover colonized by arbuscular mycorrhizal fungi

Ecological stoichiometry has been widely applied in aquatic ecosystems, but has limited implications in terrestrial ecosystems. The pot experiments with Trifolium repens L. were conducted to demonstrate the relations between C: N: P, biological components and growth rate of clover colonized by arbuscular mycorrhizal (AM) fungi. The results showed that for mycorrhizal clover, N, P concentrations increased with increasing growth rate, in support of the Growth Rate Hypothesis (GRH). Mycorrhizal clover had higher P and RNA concentrations than non-mycorrhizal clover, indicating that the increase in P concentration would invest more RNA to meet the synthesis of protein. Results also indicated that the increase in N concentration with rapid growth rate may be attributed to the increase in the concentration of protein N. Underlying mechanisms driving the association of C: N: P with growth rate for symbiotic partners should help elucidate the allocation of major nutrients to cellular organs and trophic dynamics in terrestrial ecosystems.M. M. Chen, H. B. Yin, P. O’Connor, Y. S. Wang and Y. G. Zh

Arbuscular mycorrhiza symbiosis in viticulture: a review

International audienceAbstractViticulture is a major worldwide economic sector with a vine area of 7.52 million ha, wine production of 288 Mhl, and wine exports of 26 billion euros. Nevertheless, viticulture has to adapt to new challenges of pest management, such as pesticide reduction, and climate change, such as increasing droughts. Viticulture adaptation can benefit from arbuscular mycorrhiza, a plant–fungus symbiosis. Here, we review the ecosystemic services of arbuscular mycorrhiza for grapevine production. The major points are the following: (1) arbuscular mycorrhiza fungi increase grapevine growth and nutrition by a better access to soil nutrients and by activating the regulation of plant transport proteins for phosphorus (P), nitrogen (N), and other elements. (2) Arbuscular mycorrhiza fungi increase the tolerance to abiotic stresses such as water stress, soil salinity, iron chlorosis, and heavy metal toxicity. (3) Arbuscular mycorrhiza fungi protect against biotic stresses such as root diseases. (4) Arbuscular mycorrhiza fungi produce glycoproteins and a dense hyphal network that increases soil stability and save soil nutrients up to 14 % of the grape production income. (5) P fertilisation reduces mycorhization. (6) Using herbaceous plants as cover crops favors arbuscular mycorrhiza fungi

Ordovician ash geochemistry and the establishment of land plants

<p>Abstract</p> <p>The colonization of the terrestrial environment by land plants transformed the planetary surface and its biota, and shifted the balance of Earth’s biomass from the subsurface towards the surface. However there was a long delay between the formation of palaeosols (soils) on the land surface and the key stage of plant colonization. The record of palaeosols, and their colonization by fungi and lichens extends well back into the Precambrian. While these early soils provided a potential substrate, they were generally leached of nutrients as part of the weathering process. In contrast, volcanic ash falls provide a geochemically favourable substrate that is both nutrient-rich and has high water retention, making them good hosts to land plants. An anomalously extensive system of volcanic arcs generated unprecedented volumes of lava and volcanic ash (tuff) during the Ordovician. The earliest, mid-Ordovician, records of plant spores coincide with these widespread volcanic deposits, suggesting the possibility of a genetic relationship. The ash constituted a global environment of nutrient-laden, water-saturated soil that could be exploited to maximum advantage by the evolving anchoring systems of land plants. The rapid and pervasive inoculation of modern volcanic ash by plant spores, and symbiotic nitrogen-fixing fungi, suggests that the Ordovician ash must have received a substantial load of the earliest spores and their chemistry favoured plant development. In particular, high phosphorus levels in ash were favourable to plant growth. This may have allowed photosynthesizers to diversify and enlarge, and transform the surface of the planet.</p